Stable, aqueous epoxy resin dispersions, processes for their preparation, and their use

ABSTRACT

A stable, aqueous epoxy resin dispersion including: (A) an epoxy resin prepared by condensation of at least one epoxide compound having on average at least two epoxide groups per molecule, with an aralkylated polyhydroxy aromatic compound obtained by reaction of a polyhydroxy aromatic compound with an aromatic compound which carries an alkenyl group; (B) a dispersant; and water, is useful, for example, in a coating or adhesive.

This application is a division of application Ser. No. 08/493,548, filedJun. 22, 1995, U.S. Pat. No. 5,616,634.

BACKGROUND OF THE INVENTION

It is known to prepare stable, aqueous dispersions of synthetic resinsby emulsifying corresponding monomers or oligomers in an aqueous medium,using appropriate dispersants, such as emulsifiers and surfactants, andthen carrying out a polymerization reaction. In this way it is possible,for example, to prepare aqueous dispersions of acrylate resins byemulsion polymerization.

In the case of polycondensation products, such as epoxy resins, whichare difficult or even impossible to prepare by emulsion condensation, itis necessary, however, to prepare aqueous dispersions by dispersing theresin in water. So-called secondary dispersions of this kind aregenerally highly unstable, separate after only a short time, and in mostcases also display poor film-forming properties.

According to EP-B 0 081 163 corresponding to U.S. Pat. No. 4,415,682,polyalkylene glycol derivatives are employed as nonionic dispersants toform stable, aqueous epoxy resin dispersions. Average particle sizes ofbelow 1 μm can be achieved. The coatings obtained with thesedispersions, however, are unsatisfactory in numerous properties.

EP-A 0 051 483 corresponding to U.S. Pat. No. 4,315,044 describes epoxyresin dispersions of self-emulsifying epoxy resins which comprisepolyalkylene glycol glycidyl ethers and also, if desired, a monoepoxideas reactive diluent. The maximum particle size is described as about 3μm. Films prepared from these dispersions and suitable curing agentspossess, due to the content of the relatively slow-reacting polyalkyleneglycol glycidyl ethers and, if desired, monoepoxides, which act as chainterminators, a relatively soft surface which restricts the utility ofthe epoxy dispersions.

U.S. Pat. No. 4,423,201 describes the preparation of self-emulsifyingepoxy resins from diglycidyl ethers of aromatic polyols, from aromaticpolyols and from reaction products of long-chain, aliphatic polyetherglycols with diisocyanates and aromatic polyols. The dispersion of theseresins in water, however, is possible only with the aid of relativelylarge quantities of organic solvents. In addition, the particle sizesobtained are relatively high. The coatings produced using these epoxyresin dispersions, moreover, are relatively soft.

German application DE-A 41 28 487 corresponding to U.S. Pat. No.5,236,974 describes a process for the preparation of aqueous epoxy resindispersions which comprise, as epoxy resin, a condensation product ofaromatic and aliphatic polyglycidyl compounds with aromatic polyols,and, as dispersant, a condensation product of aliphatic polyols withepoxide compounds. These dispersions exhibit excellent shear stabilityand storage stability and are outstandingly suitable for cold-curingcoatings, especially for corrosion prevention and coating applications.

German application DE-A 43 09 639 corresponding to U.S. Pat. No.5,424,340 describes systems of analogous composition which are intendedfor use in heat-curing coating systems, especially for the interiorcoating of tins for food.

A further development of the two latter unpublished applications is seenin the preparation of absolutely solvent-free epoxy resin dispersions bythe so-called monomer process. German patent application DE-A 43 27 493corresponding to CA 2,125,254 describes the process and the preparationof such dispersions, which are in the form of epoxide-addition polymerhybrid dispersions and have further technical advantages in comparisonwith pure epoxy resin dispersions, such as their freedom from solvent,higher stability of the coatings, and greater possibility of variationvia the choice of the monomers.

Since the solids present in these dispersions represents physicalmixtures, produced in situ, of epoxy resin and polymer, and since thechoice and, in particular, the quantity of the monomers is restricted bythe compatibility of the corresponding polymer with the epoxy resin,there is a need to find a manner of improving the compatibility betweenepoxide component and polymer component. Particularly good connection ofthe two components in the coating can be achieved with theabovementioned dispersions if, by appropriate choice of the functionalgroups of the polymer, co-crosslinking is able to take place during thecuring reaction.

However, it would be desirable, by appropriate modification of the epoxyresin, for the compatibility with the addition polymer to be improvedeven prior to and independently of the curing reaction, thereby enablinga distinct increase in the content of relatively inexpensive polymercomponent.

SUMMARY OF THE INVENTION

An object of the present invention is therefore to modify an epoxy resincomponent in such a way that its compatibility with addition polymerscomprising vinyl monomers is considerably improved.

It is also an object of the invention to provide stable, aqueous epoxyemulsions having desired particle size and being preferablysubstantially free of organic solvent, methods of their preparation, andmethods for their use.

In accordance with these objectives, there is provided a stable, aqueousepoxy resin dispersion including

(A) an epoxy resin formed by condensation of

(A-1) at least one epoxide compound having on average at least twoepoxide groups per molecule, with

(A-2) an aralkylated polyhydroxy aromatic compound obtained by reacting

(A-2a) a polyhydroxy aromatic compounds with

(A-2b) an aromatic compounds which carry an alkenyl group,

(B) a dispersant and water.

In accordance with other aspects of the invention, there is provided aprocess for the preparation of a stable, aqueous epoxy resin dispersionwhich includes preparing a modified epoxy resin (A) from the epoxidecompound (A1) and the aralkylated polyhydroxy aromatic compound (A2),dispersing the modified epoxy resin (A) in water with the addition of adispersant (B) and of at least one olefinically unsaturated monomer(C1), and polymerizing (C1) by adding a radical-forming initiator.

Further objects, features, and advantages of the present invention willbecome apparent from the detailed description of preferred embodimentsthat follows.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In accordance with the present invention, there is provided stableaqueous emulsions comprising,

(A) an epoxy resin prepared by condensation

(A1) of an epoxide compound having on average at least two epoxidegroups per molecule and, a preferred epoxide equivalent weight of from100 to 2000 g/mol, or preferably a mixture of two or more suchcompounds, with

(A2) one or more aralkylated polyhydroxy aromatic compounds obtained byreacting

(A2a) one or more aromatic polyols (polyhydroxy aromatic compounds )with

(A2b) one or more aromatic compounds which carry an alkenyl group,

(B) a dispersant.

The dispersant may be any desired dispersant which is effective, but ispreferably

(B1) a condensation product of

(B1a) a polyol, preferably having a weight-average molecular mass(M_(w)) of from 200 to 20,000 g/mol, and

(B1b) an epoxide compound having on average at least two epoxide groupsper molecule, and preferably an epoxide equivalent weight of from 100 to2000 g/mol, and

(B2) if desired, further, preferably nonionic surfactants.

The epoxy resin dispersion of the invention may also include

(C) if desired, a diluent. While any desired diluent may be used, it ispreferably selected from

(C1) olefinically unsaturated, otherwise inert or, if desired,functional monomers that are capable of undergoing free-radicalpolymerization or copolymerization,

(C2) low molecular weight, liquid, epoxy-functional compounds (so-calledreactive diluents), and

(C3) organic solvents.

The epoxy resin dispersion also contains

(D) water; and

(E) if desired, conventional additives, curing agents, and/or curableresins.

The term epoxide equivalent weight refers to the molecular mass dividedby the number of epoxide groups per molecule.

The weight ratio of modified epoxy resin (A) to addition polymers formedfrom monomer (C1) (assuming (C1) is present) is generally from 99.5:0.5to 20:80, preferably between 5:95 and 50:50. The polymer from monomer(C1) may comprise monomers whose functional groups are able to reactwith the intended curing agent or, at elevated temperature, with theepoxide groups, preferably in a quantity of from 2.5 to 25% based on themass of polymer from monomer (C1).

The proportion of low molecular weight epoxide compounds (C2) can bevaried as desired but, when present, is generally up to 25%, preferably1 to 20%, based on the sum of the masses of components (A) and (C1) (ifpresent).

The content of dispersant (B) is based on the sum of the masses of allcomponents of the dispersion which are not soluble in water, i.e., onthe epoxy resin (A), the polymer from (C1) (if present) and, if present,reactive diluents (C2), and is, an effective amount to give thedispersion effect and is generally between 1 and 25%, preferably between2 and 15%. The ratio by mass of the components of the dispersant is inthe case of (B1):(B2) generally between 0:100 and 100:0, preferably morethan 75:25.

The solids content by mass of the dispersion according to the inventionmay be controlled as desired, and is generally between 30 and 90%, butpreferably from 55 to 75%. The dispersion may contain up to 10% ofsolvent (C3) based on the mass of the dispersion in the supply form, butpreferably is free from solvent. In this context, stable means that nosedimentation occurs in the dispersion upon storage at 20° C. for atleast 3 weeks.

The invention also provides a process for the preparation of modifiedepoxy resin dispersions. Any desired process can be used. A particularlyuseful process comprises first synthesizing, if desired, the modifiedpolyphenols (A2) as described above, then preparing epoxy resin (A) bycondensation of the two components (A1) and (A2), generally at elevatedtemperatures in the presence of a condensation catalyst. Thecondensation reaction is preferably carried out in two stages if two ormore epoxide compounds (A1) are used, then adding the dispersant (B)and, if desired, diluent (C) and, thereafter, adding appropriatequantities of water (D) to the resulting mixture at from, for example,30° to 100° C. If the diluent which has been used includes monomersaccording to (C1), emulsion polymerization of the finished dispersion,which possibly may not yet have been diluted completely with the totalquantity of water (D), is carried out in order to produce the additionpolymer. Subsequently, if desired, further components according to (E)can be added.

In addition, however, it is also acceptable to react the (poly)phenolsmentioned under (A2a) with a substoichiometric quantity of epoxidecompounds according to (A1), and only then to modify these relativelyhigh molecular weight products with vinyl compounds (A2b) before finallypreparing the modified epoxy resin (A) using a stoichiometric excess ofepoxide compounds (A1).

The invention also provides for the use of these epoxy resin dispersionsfor the production of, for example, coating materials, coatingcompositions, molding compounds, adhesives and curable compositions.

The epoxy resin (A) of the dispersions according to the inventionpreferably has an epoxide equivalent weight of from 350 to 4000 g/mol,in particular from 400 to 2000 g/mol. The average particle size of thedispersed resin is generally not higher than than 1.0 μm and ispreferably from 0.2 to 0.8 μm. The proportion by mass of this resin inthe dispersion is generally from about 20 to 75%, preferably from about25 to 65%.

The 1,2-epoxide compounds (A1) and (B1) preferably are independentlypolyepoxides which on average have at least two epoxide groups permolecule. Any such epoxides or mixtures thereof are useful. Theseepoxide compounds may be either saturated or unsaturated and may bealiphatic, cycloaliphatic, aromatic and/or heterocyclic and may alsocontain hydroxyl groups. Moreover, they may comprise those substituentsand/or functional groups which do not bring about any troublesomesecondary reactions under the conditions of mixing or reaction, examplesincluding alkyl or aryl substituents, ether groups, and the like.

The epoxide compounds are preferably polyglycidyl ethers based onpolyhydric, preferably dihydric, alcohols, phenols, hydrogenationproducts of these phenols and/or based on novolaks (reaction products ofmono- or polyhydric phenols with aldehydes, especially formaldehyde, inthe presence of acidic catalysts). The epoxide equivalent weights ofthese epoxide compounds are preferably between 90 and 500 g/mol, inparticular between 100 and 350 g/mol.

Examples of polyhydric phenols include resorcinol, hydroquinone,2,2-bis(4-hydroxyphenyl)propane (bisphenol A), isomer mixtures ofdihydroxydiphenylmethane (bisphenol F),4,4'-dihydroxydiphenylcyclohexane,4,4'-dihydroxy-3,3'-dimethyldiphenylpropane, 4,4'-dihydroxybiphenyl,4,4'-dihydroxybenzophenone, 1,1-bis(4-hydroxyphenyl)ethane, 2,2-bis4-(2-hydroxypropoxy)phenyl!propane, 1,1-bis(4-hydroxyphenyl)isobutane,2,2-bis(4-hydroxy-3-tert-butylphenyl)propane,bis(2-hydroxynaphthyl)methane, 1,5-dihydroxynaphthalene,tris(4-hydroxyphenyl)methane, bis(4-hydroxyphenyl) ether,bis(4-hydroxyphenyl) sulfone and the like, and also the halogenation andhydrogenation products of the abovementioned compounds. Bisphenol A isparticularly preferred in this context.

Examples of polyhydric alcohols include ethylene glycol, diethyleneglycol, triethylene glycol, polyethylene glycols (degree ofpolymerization preferably n=1 to 35), 1,2-propylene glycol,polypropylene glycols (n=1 to 15), 1,3-propylene glycol, 1,4-butanediol,1,5-pentanediol, 1,6-hexanediol, 1,2,6-hexanetriol, glycerol,neopentylglycol, trimethylolethane and trimethylolpropane. Polypropyleneglycols (degree of polymerization n=8 to 10) are particularly preferred.

It is also acceptable to use polyglycidyl esters of polycarboxylicacids, which are obtained by reacting epichlorohydrin or similar epoxycompounds with an aliphatic, cycloaliphatic or aromatic polycarboxylicacid, such as oxalic acid, succinic acid, adipic acid, glutaric acid,phthalic acid, terephthalic acid, hexahydrophthalic acid,2,6-naphthalenedicarboxylic acid and dimerized linolenic acid. Examplesare diglycidyl adipate, diglycidyl phthalate and diglycidylhexahydrophthalate.

A detailed listing of suitable epoxide compounds can be found in thehandbook "Epoxidverbindungen und Epoxidharze" Epoxide compounds andepoxy resins! by A. M. Paquin, Springer Verlag, Berlin 1958, chapter IVand in Lee, Neville, "Handbook of Epoxy Resins", McGraw-Hill Book Co.,1967, chapter 2. Both of these are hereby incorporated by reference intheir entireties. The epoxide compounds mentioned may be employedindividually or in a mixture for (A1) and (B1), and (A1) and (B1) can bethe same or different.

Any polyhydroxy aromatic compounds or mixtures thereof can be used as(A2a). Examples of polyhydric (poly)phenols (A2a) include the followingcompounds: phloroglucinol, pyrogallol, hydroxyhydroquinone,1,4-dihydroxynaphthalene and its positional isomers, for example, 1,2-,1,3-, 1,5- and 1,6-dihydroxynaphthalene, 2,2'-dihydroxybiphenyl and itspositional isomers, for example, 4,4'- and 2,5-dihydroxybiphenyl,3,3'-dihydroxy-2,2'-bipyridyl, hydroquinone, resorcinol,dihydroxyanthraquinone (e.g., quinizarine, anthraflavic acid),pyrocatechol, bis(2-hydroxyphenyl)methane, bis(4-hydroxyphenyl)methane,2,2-bis(2-hydroxyphenyl)propane, 2,2-bis(4-hydroxyphenyl)propane(bisphenol A), 4,4-bis(4-hydroxyphenyl)valeric acid and the amidethereof, bis(4-hydroxyphenyl) sulfone, bis-(4-hydroxyphenyl) sulfide,2,2-bis(4-hydroxyphenyl)acetic acid and the amide thereof.

All of the polyhydroxy aromatic compounds mentioned for the epoxidecompound (A1) are also suitable for use. The (poly)phenols mentioned maybe employed individually or in a mixture. Particular preference is givento bisphenol A, bisphenol F, resorcinol, phenol, and o- or p-alkylphenol(alkyl=C₁ -C₁₈).

The vinyl compounds (A2b) include any such compound, for example,styrene, α-methylstyrene, ortho-, meta- and para-methylstyrene, ortho-,meta- and para-ethylstyrene and ring-substituted mono-, di- andtrihalostyrenes such as p-bromostyrene, p-chlorostyrene,2,4-dibromostyrene, 2,4-dichlorostyrene and 2,4,6-trichlorostyrene.

Also useful but less preferred are vinyl esters (for example, ofVersatic® acid(s): Veova® 10, Veova® 9, Veova® 5, from Shell; vinylacetate, vinyl propionate, vinyl 2-ethylhexanoate) and vinyl ethers (forexample, of methanol, ethanol, propanol, isobutanol, octadecanol,tert-butanol, cyclohexanol, and the mono- and divinyl ethers of ethyleneglycol, 1,2-propanediol and 1,3-propanediol, 1,4-butanediol,1,6-hexanediol, tetraethylene glycol, Pluriol®-E-200,polytetrahydrofurandiol, 2-diethylaminoethanol and aminopropanol, itbeing possible for the amino group to be present in blocked form, ifdesired, as ketimine).

Other suitable but less preferred vinyl compounds include esters ofacrylic or methacrylic acid with monoalcohols containing 1 to 18 carbonatoms, for example, t- or n-butyl methacrylate, methyl methacrylate,isobutyl acrylate, 2-ethylhexyl acrylate or t- or n-butyl acrylate,hydroxy-C₂₋₄ -alkyl acrylates, hydroxyethyl (meth)acrylate and/orhydroxypropyl (meth)acrylate and further compounds mentioned below under(C1).

Furthermore, it is also possible to employ reaction products of(mono)hydroxy-functional vinyl ethers or esters or (meth)acrylates (seeabove) with diisocyanates (cf. EP-A 0 296 507 incorporated by referenceherein), and (bis)phenols urethane-modified in this way.

Particular preference for (A-2) is given to reaction products of(poly)phenol and vinyl compound which contain, on average, from 1.5 to 3phenolic OH groups per molecule.

The polyols (B1a) include any desired polyols, but are preferablypolyetherpolyols (polyoxyalkylene glycols) having weight-average molarmasses (M_(w) ; gel permeation chromatography, polystyrene standard) ofpreferably between 600 and 12,000 g/mol, in particular from 2000 to 8000g/mol and OH numbers which are advantageously from 10 to 600, preferablyfrom 15 to 120, mg of KOH/g. These polyetherpolyols preferably possessonly terminal, primary OH groups. Examples in this context are blockcopolymers of ethylene oxide and propylene oxide, and polyethylene,polypropylene and polybutylene glycols, it also being possible to employmixtures of the respective polyalkylene glycols. Polyethylene glycolsare preferably used.

Suitable epoxide compounds (B1b) include any in the art as well as allof the compounds mentioned above under (A1) .

The dispersant (B1) is preferably prepared by condensation of theabovementioned polyetherpolyols (B1a) with the polyglycidyl ethers (B1b)in the presence of suitable catalysts at, for example, from 50° to 200°C., preferably from 90° to 170° C., with the ratio of the number of OHgroups to that of the epoxide groups generally being from 1:0.8 to1:1.5, preferably from 1:0.95 to 1:1.25, and the epoxide equivalentweight of the condensation product being at least 5000 g/mol, preferablyfrom 100,000 g/mol to 400,000 g/mol. In this way it is possible, forexample, to react hydrophobic epoxide compounds (e.g., polyethyleneglycol diglycidyl ether) with hydrophobic polyols (e.g., bisphenol A)or, preferably and conversely, hydrophobic epoxide compounds (e.g.,bisphenol A diglycidyl ether) with hydrophilic polyols (e.g.,polyethylene glycol). Products of this kind are described in DE-C 36 43751 and DE-A 41 28 487 corresponding to U.S. Pat. No. 5,236,974, bothwhich are hereby incorporated by reference.

Suitable catalysts for this condensation reaction include stronginorganic and organic bases, for example, sodium hydroxide, potassiumhydroxide, lithium hydroxide, barium hydroxide, strontium hydroxide,alkali metal alcoholates such as sodium methylate, lithium methylate,sodium ethylate and potassium dodecylate, and the alkali metal salts ofcarboxylic acids, for example, sodium stearate and lithium stearate.Also suitable are strong inorganic and organic Bronsted acids, forexample, phosphoric acid, tetrafluoroboric acid and toluene- orbenzenesulfonic acid. Lewis acids can also be used as catalysts.Examples include tin tetrachloride, titanium tetrachloride, titaniumtetraisopropylate, triethyloxonium tetrafluoroborate, and also borontrifluoride and its complexes, for example, with phosphoric acid, aceticacid (1:1 and 1:2), methanol, diethyl ether, tetrahydrofuran, phenol,ethylene glycol monoethyl ether, polyethylene glycol (for example, ofmolar mass 200 g/mol), dimethyl sulfoxide, di-n-butyl ether, di-n-hexylether, succinic acid and aliphatic, cycloaliphatic and araliphaticamines, and also nitrogen-containing heterocycles.

As catalysts it is preferred to employ BF₃ -diethyl etherate, BF₃-acetic acid adduct and aqueous tetrafluoroboric acid. The quantity ofcatalyst is generally from 0.1 to 5%, preferably from 0.1 to 1%, basedon the mass of the reaction mixture. To facilitate its addition, thecatalyst may be diluted in a solvent such as diethyl ether, a glycolether or cyclic ether, ketones and the like.

In order to prepare the condensation product (B1) the mixtures to bereacted, comprising compounds containing hydroxyl groups and compoundscontaining epoxide groups, are heated to the temperature at which thecondensation takes place at a sufficient rate, i.e., in from 30 minutesto 5 hours. The reaction is advantageously monitored by way of theincrease in the epoxide equivalent weight, which indicates a reductionin the number of epoxide groups. The reaction can be terminated bycooling to below the reaction temperature.

The condensation product (B1) obtained in this way can be used as such(100% strength) as dispersant (B) for the preparation of the dispersionsaccording to the invention. Preferably, however, for reasons of betterhandling, a mixture is prepared of from 20 to 99%, preferably from 40 to60%, of the condensation product (B1) and an aqueous medium consistingof (based on the overall mixture) up to 50%, preferably from 1 up to30%, of an organic solvent (C3) and from 1 to 80%, preferably from 15 to60%, of water (D), and this mixture is used as dispersant.

Any desired solvent (C3) can be used. (C3) is optional and preferably isnot present. Thus, a solvent-free dispersion can be produced.Particularly suitable organic solvents in accordance with component (C3)include glycols, mono- and diethers and mono and diesters of glycolswith alcohols and acids, aliphatic alcohols with linear or branchedalkyl radicals of 1 to 12 carbon atoms, cycloaliphatic and araliphaticalcohols, and also esters and ketones, it being possible to employ thesesolvents individually or in a mixture. Examples of solvents which may bementioned include: ethylene glycol, ethylene glycol monomethyl ether,ethylene glycol dimethyl ether, butylglycol, methoxypropanol,ethoxypropanol, ethanol, 1- and 2-propanol, butanol, cyclohexanol,benzyl alcohol, ethyl acetate, acetone and also methyl isobutyl ketone.Preference is given to employing butylglycol, methoxypropanol,ethoxypropanol, 2-propanol and/or benzyl alcohol.

In addition to the dispersant (B1) it is also possible to use otherdispersants (B2) of the anionic, cationic and--preferably--nonionictype. Any known surfactants can be used. Suitable anionic surfactantsinclude alkylbenzenesulfonates, primary and secondary alkanesulfonates,α-olefinsulfonates, alkyl sulfates and alkyl ether sulfates, andsuitable cationic surfactants include quaternary ammonium compounds, andin this context the ionic groups must not interact with the epoxidegroups. It is preferred, however, to use nonionic surfactants such asethoxylated or eth/propoxylated alcohols, oxo alcohols, alkylphenols(e.g., Arcopal® from Hoechst), castor oils, esters, glycerol stearates,fatty acids, fatty amines, fatty alcohols, or else, for example,ethylene oxide-propylene oxide block copolymers (e.g., Pluronic® fromBASF).

The emulsifiers which are specifically described for the dispersion ofepoxy resins can also be employed, for example, those described in U.S.Pat. No. 4,423,201 and U.S. Pat. No. 4,446,256 (products of polyalkyleneglycols, diisocyanates and bisphenols), EP-A 0 497 404 (products ofalkoxypolyalkylene glycols, anhydrides and alkylene oxides, epoxyalcohols or diglycidyl ethers), WO 91/10695 corresponding to CA2,072,076 (products of polyglycidyl ethers, bifunctional compounds andalkoxypolyalkylene glycols), EP-A 0 109 173 corresponding to U.S. Pat.No. 4,421,906 (products of polyoxyalkylenepolyamines and epoxy resins)and DE-A 41 36 943 (products of polyalkylene glycols with diisocyanatesand polyepoxides).

The optional diluent (C) may be composed of monomers (C1) which arecapable of undergoing polymerization, low molecular weight, liquidepoxide compounds--so-called reactive diluents--(C2), and/or organicsolvents (C3).

Suitable monomers (C1) include all ethylenically unsaturated compoundswhich are capable of undergoing free-radical polymerization in emulsionand do not give rise to unwanted interaction with the existing epoxyresin dispersion at room temperature. Such monomers include acrylic,methacrylic and higher alkylacrylic acids, and the alkyl esters thereof(C₁ - to C₁₈ -alkyl (meth)acrylates, for example, methyl acrylate andmethacrylate, ethyl acrylate and methacrylate, n- and isopropyl acrylateand methacrylate, n-, iso- and tert-butyl acrylate, n- and tert-butylmethacrylate, 2-ethylhexyl acrylate and methacrylate,4-tert-butylcyclohexyl acrylate, isobornyl acrylate and methacrylate)and derivatives (e.g., acrylonitrile), but also vinyl derivatives (e.g.,styrene, α-methylstyrene, vinyltoluenes, vinyl acetate, vinyl chloride,vinylidene chloride, N-vinylpyrrolidone) and α,β-unsaturated carboxylicacids such as maleic acid, fumaric acid, itaconic acid and derivativesthereof, and also alkenes such as isoprene and butadiene.

The monomers may also contain functional groups which participate in thecuring reaction of the epoxy resin which is desired later. Examples ofsuitable monomers include glycidyl- and hydroxyl-functional monomers(e.g., glycidyl methacrylate, 2-hydroxybutyl acrylate, 4-hydroxybutylacrylate, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate,2-hydroxypropyl acrylate, hydroxypropyl methacrylate, and the like).Also, amido-functional compounds (e.g., acrylamide) or N-methylolmonomers (e.g., N-methylolacrylamide) may be used. Finally,polyfunctional monomers, whether with respect to the polymerization orthe curing process, may also be present, examples being 1,6-hexanedioldiacrylate and divinylbenzene.

The monomers (C1) may be added as the total quantity all at once priorto the dispersion in water, and thus act to reduce the viscosity andfacilitate the dispersion operation, or, given a relatively highproportion of polymer, a portion thereof can be present during thedispersion operation while the remainder is metered in continuouslyduring the emulsion polymerization of (C1). In this way core-shellparticles can be produced in a targeted manner. The presence of themonomers during dispersion has the advantage that the viscosity maximumin the course of the phase inversion W/O→O/W (water-in-oil tooil-in-water) need not be reduced by inert solvents which remain in thefinished dispersion, as was described in EP-A 0 272 595 corresponding toU.S. Pat. No. 4,886,845. Thus it is possible to formulate completelysolvent-free dispersions--a further considerable improvement on theprior art. However, an excessive monomer content during the dispersionoperation may reduce the viscosity too much, and the shear force to beapplied for the dispersion operations would no longer be able to bedeveloped. For this reason, if appropriate, it is desirable to dividethe quantity of monomers into two or more appropriate portions.

If it is intended to co-crosslink the polymer in the course of thecuring reaction, then functional co-monomers should be employed in (C1).Preferred monomers for cold-curing systems (amine curing agents) arethose containing glycidyl groups (e.g., glycidyl methacrylate);preferred monomers for heat-curing systems are those containing acidgroups (for example, methacrylic acid, which reacts on baking with theepoxide groups of (A) and, if present, (C2)), or OH-functional monomers(for example, hydroxyethyl methacrylate, which reacts on baking withmethylol or acid groups of the curing agent).

Low molecular weight, liquid, epoxy-functional compounds (C2) which areuseful include mono- and diglycidyl ethers, which are known inter aliaby the term reactive diluents, examples being para-tert-butylphenylglycidyl ether, n-butyl glycidyl ether, phenyl glycidyl ether,ortho-cresyl glycidyl ether, butanediol diglycidyl ether, hexanedioldiglycidyl ether, neopentylglycol diglycidyl ether,dimethylolcyclohexane diglycidyl ether, 2-ethylhexyl glycidyl ether,higher alkyl glycidyl ethers, and the like (e.g., the reactive diluentsof the series Grilonit® RV from Ems, Epodil® from Anchor or Eurepox® RVfrom Schering), Versatic® acid glycidyl esters (Cardura® E 10 fromShell), liquid polyoxyalkylene diglycidyl ethers (e.g., Beckopox® EP 075from Hoechst), and also liquid epoxy resins such as, for example,diglycidyl ethers of bisphenol A and of bisphenol F. Component (C2) isreferred to below for reasons of simplicity as reactive diluent.Preferred reactive diluents are hexanediol diglycidyl ether andpara-tert-butylphenyl glycidyl ether. The molar mass of these compoundsis generally below 800 g/mol.

In addition to the solvents mentioned above for (B), suitable organicsolvents (C3) also include aromatic compounds such as toluene or xylene.The solvents may be employed individually or in mixture. Preferredsolvents are once again butylglycol, methoxypropanol, ethoxypropanol,2-propanol and/or benzyl alcohol.

As conventional additives (E), which may optionally be present in thecombinations according to the invention, mention is made, for example,of the conventional coatings additives, such as pigments, pigmentpastes, antioxidants, leveling agents, thickeners, antifoams and/orwetting agents, reactive diluents, fillers, catalysts, preservatives andprotective colloids. These additives, like the further curable resinsand the curing agents which are described later on, can be added to thedispersion, if desired, not until directly prior to processing.

The invention also provides a process for the preparation of the epoxyresin dispersions according to the invention. In this process the epoxyresin (A) can be prepared by condensation of components (A1) and (A2) atelevated temperatures, in general from 100° to 220° C., preferably from150° to 180° C., in the presence of a catalyst which accelerates thecondensation.

If two or more epoxide compounds (A1) are employed, then thecondensation reaction is preferably carried out in two stages such that,in a first reaction, one or more components (A1) are reacted with thecomponents according to (A2) in a proportion such that this firstcondensation product has an epoxide equivalent weight of more than 5000g/mol, preferably more than 20,000 g/mol, and still contains freephenolic groups, and, in a further condensation reaction, this firstcondensation product is reacted with further epoxide compounds accordingto (A1), so that finally the desired epoxy resin (A) is obtained.

Examples of suitable condensation catalysts include phosphines such astriphenylphosphine, phosphonium salts such as benzyltrimethylphosphoniumchloride, tertiary amines such as N,N-dimethylbenzylamine, quaternaryammonium salts such as tetramethylammonium chloride, alkali metalhydroxides such as sodium hydroxide and lithium hydroxide, alkali metalcarbonates such as sodium carbonate and lithium carbonate, alkali metalsalts of organic acids, for example, sodium formate, lithium benzoateand lithium stearate, and Lewis acids, for example, boron trifluorideand its complexes, titanium tetrachloride, tin chloride andtriethyloxonium tetrafluoroborate.

Subsequently, the dispersant (B) and, if desired, diluents according to(C) are added to the epoxy resin (A) at temperatures of, for example,from 60° to 200° C., preferably from 70° to 120° C., and the mixture isstirred, for example, from 15 to 180 minutes, preferably from 30 to 90minutes.

Thereafter, the appropriate quantity of water (D) is metered in withvigorous stirring, preferably in two or more portions, at temperaturesof, for example, from 30° to 100° C., preferably from 50° to 90° C.,thereby producing the aqueous dispersion.

The diluent (C) which may be used is generally added as the total amountall at once prior to the dispersion in water, and thus acts to reducethe viscosity and facilitate the dispersion operation, or, in the caseof a relatively large amount, it may be present in part during thedispersion operation, and the remainder is added once dispersion hasbeen carried out. In this context it is not necessary for the twoportions to be identical in terms of the nature and composition ofcomponents (C1), (C2) and (C3). The presence of the diluent (C1) and/or(C2) during the dispersion has the effect that the viscosity maximum inthe phase inversion W/O→O/W need not be reduced by inert solvents whichremain in the finished dispersion, as was described in DE-A 41 28 487corresponding to U.S. Pat. No. 5,236,974. It is therefore possible,without solvents according to (C3), to formulate completely solvent-freedispersions--a further considerable improvement on the prior art.However, an excessive content during the dispersion operation wouldreduce the viscosity too much, and it would no longer be possible tobuild up the shear force to be applied for the dispersion operations. Itmay therefore be necessary to divide the total amount into twoappropriate portions.

Reactive diluent (C2) can be used, moreover, in order to control theapplications-related properties of the dispersion, for example,reduction of the minimum film-forming temperature, extension of the potlife, improvement in gloss, shear stability and stability to freeze-thawcycles, specific influencing of hardness and elasticity, etc. Theadvantage over the use of organic solvents is that these reactivediluents are incorporated into the film during the curing reaction andthus do not lead to the unwanted emission of organic components; theclaim to freedom from solvent thus remains intact. The addition of thereactive diluent prior to the dispersion process has the substantialadvantage that this diluent is emulsified markedly better and with lesseffort than in the case of subsequent addition to the finisheddispersion, thereby leading to an improvement in the quality of thecoating. In this case, reactive diluent and base resin are probablypresent in conjoint micelles, a state which subsequent incorporation andhomogenization of the reactive diluents is unable to achieve. Thecontent of reactive diluent should be added on to the solids content ofthe binder and/or the coating material.

In a preferred process, when epoxide-polyacrylate dispersions areprepared, at temperatures of from 60° to 200° C., preferably from 70° to120° C., to the epoxy resin (A) are added the monomers (C1)--stabilizedif appropriate with suitable inhibitors known to those skilled in theart--and, if desired, reactive diluent (C2) or an appropriate portion,then the dispersants (B1) and, if desired, (B2), followed if desired byorganic solvent (C3), and the mixture is stirred for from 15 to 180minutes, preferably from 30 to 90 minutes. As an alternative theaddition of the monomers can be followed by carrying out a reactionbetween epoxy resin and the monomers, for example, the addition ofcarboxyl or amine monomers onto the epoxide groups or grafting ontoaliphatic carbon atoms of the epoxide components (A) and (C2), beforethe dispersant is added.

Subsequently, at temperatures of from 30° to 100° C., preferably from50° to 90° C., the appropriate quantity of water (D) is metered in withvigorous stirring, preferably in two or more portions, to form theaqueous dispersion. At this point, suitable antifoam/deaerationadditives may be added if desired. The dispersion operation isadvantageously carried out with the aid of suitable dispersingequipment, for example, a high-speed paddle stirrer, a multiple-impulsehelical stirrer, a colloid mill, a homogenizer, a dissolver or any otherrapid mixer having a high shear force. This operation is described ingreat detail in DE-A 41 28 487 corresponding to U.S. Pat. No. 5,236,974the disclosure of which is incorporated by reference herein.

This process yields an epoxy resin dispersion which comprises monomersand reactive diluent, in which emulsion polymerization is initiated atan appropriate temperature. In the case of redox initiators, theoxidizing agent is preferably incorporated by homogenization togetherwith the water of dilution, and the reducing agent is metered incontinuously; however, all conceivable variants are likewise inaccordance with the invention. If the quantity of monomer is greaterthan that required for the dispersion, then the remaining quantity ofthe monomers (C1) is also metered in at this stage, with the targetedpreparation of core-shell acrylate particles being possible here withthe aim of controlling the properties of the dispersion in a desiredmanner. The preferred temperature range for the emulsion polymerizationis from 60° to 90° C., and the reaction is monitored by determining thesolids content or by gas chromatography. Any unwanted increase inviscosity can be compensated by the subsequent metered addition ofwater.

The emulsion polymerization can be initiated at a temperature whichguarantees rapid and complete reaction and, at the same time, does notpose a threat to the dispersion. Suitable radical-forming initiators forthis reaction are heat-activatable free-radical initiators or redoxsystems, all of which are well known to those skilled in the art. It isalso possible, preferably, to employ mixtures of two or more initiators.

Thermal initiators include peroxides, hydroperoxides, per-esters anddiazo compounds, examples being dibenzoyl peroxide, acetyl peroxide,benzoyl hydroperoxide, tert-butyl hydroperoxide, di-tert-butyl peroxide,lauroyl peroxide, butyryl peroxide, diisopropylbenzene hydroperoxide,cumene hydroperoxide, paramenthane hydroperoxide, diacetyl peroxide,di-α-cumyl peroxide, dipropyl peroxide, diisopropyl peroxide,isopropyl-tert-butyl peroxide, butyl-tert-butyl peroxide, dilauroylperoxide, difuroyl peroxide, ditriphenylmethyl peroxide,bis(p-methoxybenzoyl) peroxide, p-monomethoxybenzoyl peroxide, rubreneperoxide, ascaridole peroxide, tert-butyl peroxybenzoate, diethylperoxyterephthalate, propyl hydroperoxide, isopropyl hydroperoxide,n-butyl hydroperoxide, tert-butyl hydroperoxide, cyclohexylhydroperoxide, trans-decalin hydroperoxide, α-methylbenzylhydroperoxide, α-methyl-α-ethylbenzyl hydroperoxide, tetralinhydroperoxide, triphenylmethyl hydroperoxide, diphenylmethylhydroperoxide, 2,5-dimethyl-2,5-bis(2-ethylhexanoylperoxy)hexane,1,1-bis(tert-butylperoxy)cyclohexane and tert-butyl perbenzoate.

Redox systems may be selected from oxidants such as, for example,hydrogen peroxide, tert-butyl hydroperoxide or persulfates, incombination with reducing agents such as alpha-hydroxy ketones, ascorbicacid, hydrazine and sulfites, bisulfites, metasulfites or hydrosulfites.

Preferably, the initiators employed should be those which generate fewor no ionic compounds, so as not unnecessarily to increase thesensitivity to water of the subsequently baked films. If desired,acceleration can be brought about by employing the salts of transitionmetals which are known for this purpose. A particularly preferred systemis tert-butyl hydroperoxide/ascorbic acid.

The epoxy resin dispersions according to the invention are distinguishedon the one hand by their good storage stability, which is to beattributed to the low--for secondary dispersions--average particle size,and on the other hand, in particular, by their very low or zero contentof organic solvents.

The viscosity of these dispersions is in general between 200 and 30,000mPa·s, preferably between 750 and 7000 mPa·s.

The curing agents and further curable resins according to (E) which maybe used, are preferably not added until directly before the use of thedispersion. For the modified epoxy resins of the invention, any of thecuring agents and/or curing compounds (epoxide hardeners) which areknown for this purpose can be employed, such as basic curing agents(amine hardeners), for example, polyamines, Mannich bases, adducts ofamines with polymers, such as polyepoxides and polyamidoamines.

In addition, acidic curing agents (acid hardeners) such aspolycarboxylic acids and their anhydrides, and polyhydric phenols, canbe used. Synthetic resins containing hydroxyl and/or amino groups, suchas amine or phenolic resins, are also suitable for this purpose.

The epoxy resin dispersions according to the invention can also be curedby means of so-called latent curing agents, i.e., compounds whichdevelop their cross-linking action with regard to epoxide compounds onlyat relatively high temperatures, for example, at from 60° to 250° C.Examples of such curing agents are urea, dicyandiamide, imidazole,guanidine, hydrazide and derivatives of the compounds mentioned. Amongthese latent curing agents, preference is given to the use ofdicyandiamide.

Examples of basic curing agents, preferably for curing at roomtemperature and/or relatively low temperatures (amine cold hardeners),which are generally employed in a ratio of the number of epoxide groupsto the number of amine hydrogen atoms of 1:(0.75 to 2.0), arepolyalkyleneamines, such as diethylenetriamine, triethylenetetramine,tetraethylenepentamine, pentaethylenehexamine, and also 2,2,4- and/or2,4,4-trimethylhexamethylenediamine, bis(3-aminopropyl)amine,1,4-bis(3-aminopropyl)piperazine, N,N-bis(3-aminopropyl)ethylenediamine,neopentanediamine, 2-methyl-1,5-pentanediamine, 1,3-diaminopentane,hexamethylenediamine, and cycloaliphatic amines such as 1,2- and/or1,3-diaminocyclohexane, 1,4-diamino-3,6-diethylcyclohexane,1,2-diamino-4-ethylcyclohexane, 1,4-diamino-3,6-diethylcyclohexane,1-cyclohexyl-3,4-diaminocyclohexane, isophoronediamine and reactionproducts thereof, 4,4'-diaminodicyclohexylmethane and -propane,2,2-bis(4-aminocyclohexyl)methane and -propane,3,3'-dimethyl-4,4'-diaminodicyclohexylmethane,3-amino-1-cyclohexylaminopropane, 1,3- and1,4-bis(aminomethyl)-cyclohexane.

As araliphatic amines, use is made in particular of those which containaliphatic amino groups, for example, meta- and para-xylylenediamine orhydrogenation products thereof.

The amines mentioned may be used alone or as mixtures.

Suitable Mannich bases are prepared by the condensation of polyamines,preferably diethylenetriamine, triethylenetetramine, isophoronediamine,2,2,4- and/or 2,4,4-trimethylhexamethylenediamine, 1,3- and1,4-bis-(aminomethyl)cyclohexane, especially meta- andparaxylylenediamine, with aldehydes, preferably formaldehyde, and mono-or polyhydric phenols having at least one ring position which isreactive with respect to aldehydes, examples being the various cresolsand xylenols, para-tert-butylphenol, resorcinol,4,4'-dihydroxydiphenylmethane and 4,4'-dihydroxydiphenyl-2,2-propane,but preferably phenol.

Examples of suitable amine-epoxide adducts are reaction products ofpolyamines, for example, ethylenediamine, propylenediamine,hexamethylenediamine, 2,2,4- and/or 2,4,4-trimethylhexamethylenediamine,metaxylylenediamine and/or bis(aminomethyl)cyclohexane with terminalmono- or polyepoxides, for example, propylene oxide, hexene oxide, orcyclohexene oxide, or with glycidyl ethers such as phenyl glycidylether, tert-butyl glycidyl ether, ethylhexyl glycidyl ether, butylglycidyl ether or with glycidyl esters, such as the glycidyl ester ofVersatic® acid marketed by Shell, Cardura® E, or the polyglycidyl ethersand polyglycidyl esters mentioned under (A1) and/or (B1b).

Polyamidoamines which can be used to cure the epoxy resin dispersionsaccording to the invention are obtained, for example, by reactingpolyamines with mono- or polycarboxylic acids, for example, dimerizedfatty acids.

As amine curing agents, in addition to the abovementioned polyamines itis preferred to employ water-soluble polyoxyalkylenedi- and -polyamineshaving molar masses of from 100 to 2000 g/mol, for example, the productsmarketed by Texaco under the trade name Jeffamine®, and the readilywater-dispersible curing agents as described in DE-A 23 32 177corresponding to U.S. Pat. No. 3,870,666 and EP-B 0 000 605, in otherwords modified amine adducts, for example.

In order to obtain more rapid and/or more complete through-curing it isalso possible to heat the coatings which are obtainable from the epoxyresin dispersions according to the invention, using the amine curingagents mentioned, at from 50° to 120° C. for from 15 to 120 minutes.

As acidic curing agents, which are generally employed in a ratio of thenumber of epoxide groups to the number of carboxyl groups of from1:(0.75 to 2), water-soluble or water-miscible polycarboxylic acids aresuitable. Examples of such polycarboxylic acids includecyclopentanetetracarboxylic acid, cyclobutanetetracarboxylic acid,1,2,3,4-butanetetracarboxylic acid, tartaric acid, malonic acid, malicacid, citric acid and aconitic acid.

Further suitable compounds, if desired, are anhydrides or acidic estersof these acids with polyhydric alcohols of from 2 to 12, preferably offrom 2 to 6, carbon atoms, such as neopentylglycol, glycerol,trimethylolethane or trimethylolpropane, the alkanediols and oligomersthereof which may contain one or more ether bridges, such as ethyleneglycol, propane- and butanediols, with the esters always containing atleast two free carboxyl groups. It is also possible for thepolycarboxylic acid curing agents used to be acidic esters, having twoor more carboxyl groups, of carboxylic acids, for example, pyromelliticacid, trimellitic acid, phthalic acid, endomethylenetetra- or-hexahydrophthalic acid, maleic acid, fumaric acid and their anhydrides,where they exist, with polyhydric alcohols, for example, those mentionedabove, provided these acidic esters possess an adequate solubility ordilutability in water. As acidic curing agents it is preferred to employpolycarboxylic acids.

The curing of the epoxy resin dispersions with the acidic curing agentsmentioned is advantageously carried out at relatively high temperatures,for example, at from 60° to 220° C., preferably from 80° to 200° C., infrom 15 to 50 minutes. In order to attain more complete through-curingor to reduce the temperatures necessary for sufficient through-curing,it is also possible to add to the abovementioned acid curing agentssmall quantities of compounds which catalyze the reaction betweencarboxyl group and epoxide group. Examples of suitable compounds arestrong protonic acids such as phosphoric acid or para-toluenesulfonicacid, tertiary amines such as triethylamine, N,N-dimethylbenzylamine,nitrogen-containing heterocycles such as imidazole, pyridine andderivatives thereof, trialkyl- and triarylphosphines and appropriatephosphonium compounds, and metal salts and/or metal chelates, forexample, tin(II) octoate.

Instead of or in addition to the above-described curing agents it isalso possible to use amine and/or phenolic resins for curing, which areemployed in quantities of, for example, from 5 to 50%, preferably from10 to 35%, based on the overall mass of the solids. If desired, thedispersion is in this context further adjusted to an overall solidscontent of from 10 to 80% by adding an additional quantity of water.Examples of such amine resins are amine-aldehyde resins, i.e.,condensation products of aldehydes with melamine (melamine resins), urea(urea resins), acetoguanamine (acetoguanamine resins) or similarcompounds and/or corresponding precondensation products. Preferredaldehyde condensation products of melamine are, in particular, thealkoxymethylmelamine derivatives in which the alkyl radicals are methyl,n-butyl or isobutyl groups, preferably methyl groups, such ashexamethoxymethylmelamine, ethoxymethoxymethylmelamine,monomethylolpentamethoxymethylmelamine,dimethyloltetramethoxymethylmelamine,trimethyloltrimethoxymethylmelamine and the like, having a largelymonomeric structure, and corresponding oligomeric or polymeric products.

Phenolic resin curing agents which may be mentioned are resols,formaldehyde-phenolcarboxylic acid resins and phenolic resin precursors,preference being given to the commercially available, etherified,water-dilutable phenolic resin resols.

If desired, the dispersions containing phenolic and/or amine resin canalso have added to them acidic catalysts, such as para-toluenesulfonicacid, cyclohexanesulfamic acid, acid butyl phosphate and phosphoricacid--if desired also as (amine) salts--in order to accelerate the rateof the curing reaction, so as to give films or coatings which cure atlow temperature or in a relatively short time. The quantity of theseacidic catalysts can be, for example, 2% based on the overall mass ofsolids.

Additional, curable resins useful as optional component (E) are, forexample, resins which are dispersible in aqueous media and are based onhydroxyalkyl acrylic esters, hydroxy alkyds, polyesters, epoxy resinsand the like. The proportion of these additives may be such, forexample, that the overall solids content by mass of the mixture is fromabout 10 to 80%, preferably from 20 to 40%. The addition of such resinsenables the properties of the products produced from the dispersions tobe influenced in a great diversity of ways. Thus, for example, it ispossible to use the addition of acrylate resins to increase theyellowing resistance, whereas when alkyd resins are present there is asignificant improvement in the elasticity of the coatings preparedtherefrom.

Compared with those epoxy resin dispersions which are already known, thecoatings which are obtainable using the dispersions according to theinvention additionally possess a range of technical advantages, forexample, very low sensitivity to water, very good elasticity coupledwith improved hardness, good to very good adhesion to a wide variety ofsubstrates, and outstanding corrosion prevention in the coating ofmetallic materials.

On the basis of their outstanding technical properties which havealready been discussed, for example, in respect of adhesion, hardness,corrosion prevention, and resistance to water and chemicals, thedispersions according to the invention are suitable, in combination withappropriate curing agents and additives, for the production of coatings,intermediate coatings, coating materials, molding compositions andcurable compositions for a very wide range of applications. For example,they can be used for the production of protective and/or decorativecoatings on a very great variety of substrates, including in particularrough and porous substrates, for example, wood, mineral substrates(e.g., concrete and masonry), glass, plastics (e.g., polyethylene,polypropylene), composite materials, ceramics and pretreated ornonpretreated metals.

On the basis of their good properties the dispersions according to theinvention are also outstandingly suitable for single-layer coating. Theadhering coating layer can remain unchanged as it is, or else it can beused as an intermediate layer, i.e., a substrate for further coatings,which may in turn consist of the same coating material or a different,conventional coating material.

Because of their ready dilutability and their favorable properties, thedispersions according to the invention are also suitable for additionaluse in electrodeposition coating.

A further possible application of the dispersions according to theinvention is their use for the production of water-dilutable adhesives.They can also be employed as binders for textile, organic and/orinorganic materials.

In addition, they may serve as an additive to plastic cements.

When used as coating compositions or as predominantly aqueous coatingmaterials, application to the substrate is by any desired conventionalmethod such as, for example, by brushing, spraying, dipping or rolling.Where no curing agents are used for the cold curing, the coatings arecured by heating at from 80° to 250° C. for a time which is sufficientto effect complete curing, in general from 5 to 60 minutes.

A significant advantage is to be seen in the considerably improvedcompatibility with high-styrene polyacrylates which, moreover, may bepresent in relatively large quantities in the overall system owing tothe use of "styrenized resins".

The invention is further described with reference to the followingexamples. The examples are for illustrative purposes only and do notfurther limit the invention.

EXAMPLES

1. Preparation of modified epoxy resin dispersions

Synthesis of the base resin modified in accordance with the invention

60 g of a diglycidyl ether of polypropylene glycol 600 (A1) are reactedwith 136 g of a reaction product A-2 of 1 mol of bisphenol A (A2a) with2 mol of styrene (A2b) (OH equivalent weight about 220 g/mol) in thepresence of 0.3 g of Shell® catalyst 1201 (triphenylethylphosphoniumiodide) at 160° C. until the epoxide equivalent weight is greater than15,000 g/mol. The reaction mixture is cooled to 100° C. and then 254 gof diglycidyl ether of bisphenol A (A1, epoxide equivalent weight about185 g/mol) and 0.1 g of Shell® catalyst 1201 are added, and reaction iscarried out at 160° C. up to an epoxide equivalent weight of about 480g/mol.

1.1 Dispersion according to the invention for cold-curing systemsaccording to DE-A 41 28 487 corresponding to U.S. Pat. No. 5,236,974,which is hereby incorporated by reference.

Modified base resin, containing solvent

50 g of methoxypropanol (C3) are added at 100° C. to the base resinaccording to the invention, followed by 100 g of a 50% strength solutionof an emulsifier B1 in water/2-propanol (C3) (1:1), as described in DE-A36 43 751, hereby incorporated by reference. The resin is then dispersedwith 310 g of water D by the method described in DE-A 41 28 487corresponding to U.S. Pat. No. 5,236,974.

A storage-stable dispersion is obtained which has the followingcharacteristics:

    ______________________________________                                        viscosity (25° C., Brookfield)                                                              913 mPa · s                                     residue (1 h, 1 g, 125° C.)                                                                 54.5%                                                    epoxide equivalent weight                                                                         1013 g/mol                                                (supply form)                                                                 particle size (monomodal)                                                                          820 nm                                                   emulsifier content   10% based on solids                                      solvent content      10% based on solids                                      ______________________________________                                    

1.2 Comparison dispersion according to DE-A 43 27 493 corresponding toCA 2,125,254

Non-modified base resin, free of solvent

A base resin is prepared as in accordance with Example 1 but using thecorresponding quantity of non-styrenized bisphenol A. To 385 g of thisresin are added 138 g of a 50% strength solution of an emulsifier B1 inwater, as described in DE-A 36 43 751 corresponding to U.S. Pat. No.4,886,845, and 43 g of styrene C1. The mixture is then dispersed with320 g of water D by the method described in DE-A 41 28 487 correspondingto U.S. Pat. No. 5,236,974. Following this, polymerization is carriedout at 75° C. by the method described in DE-A 43 27 493 corresponding toCA 2,125,254 hereby incorporated by reference (see also Example 2.2).

A storage-stable dispersion is obtained which has the followingcharacteristics:

    ______________________________________                                        viscosity (25° C., Brookfield)                                                             1480 mPa · s                                     residue (1 h, 1 g, 125° C.)                                                                 56.0%                                                    epoxide equivalent weight                                                                         1078 g/mol                                                (supply form)                                                                 particle size (monomodal)                                                                          338 nm                                                   emulsifier content    8% based on solids                                      solvent content       0%                                                      ______________________________________                                    

1.3 Dispersion according to the invention according to DE-A 43 27 493.5corresponding to CA 2,125,254

Modified base resin, free of solvent

To 385 g of the base resin according to the invention are added 138 g ofa 50% strength solution of an emulsifier B1 in water, as described inDE-A 36 43 751 corresponding to U.S. Pat. No. 4,886,845, and 43 g ofstyrene (C1). The mixture is then dispersed with 320 g of water D by themethod described in DE-A 41 28 487 corresponding to U.S. Pat. No.5,236,974. Following this, polymerization is carried out at 75° C. bythe method described in DE-A 43 27 493 corresponding to CA 2,125,254(see also Example 2.2).

A storage-stable dispersion is obtained which has the followingcharacteristics:

    ______________________________________                                        viscosity (25° C., Brookfield)                                                             1810 mPa · s                                     residue (1 h, 1 g, 125° C.)                                                                 55.8%                                                    epoxide equivalent weight                                                                         1213 g/mol                                                (supply form)                                                                 particle size (monomodal)                                                                          425 nm                                                   emulsifier content    8% based on solids                                      solvent content       0%                                                      ______________________________________                                    

Applications-related properties

The dispersion 1.1 to 1.3 are mixed with an equivalent of the curingagent Beckopox® EH 623w (Hoechst, an aqueous solution of modifiedaliphatic polyamine, 80% strength) diluted with water to 40% and aredrawn onto degreased glass plates, dry film thickness 25 μm. Curing iscarried out at 26° C./40% relative atmospheric humidity.

As a commercial comparison system, the aqueous dispersion Beckopox® VEP2385w (Hoechst, an aqueous dispersion of flexibilized epoxy resin, massfraction of epoxy resin 56%, mass fraction of water 42%, mass fractionof isopropanol 2%) was also tested.

The comparison demonstrates that the compatibility of the resincomponents is considerably improved by the use of the "styrenized epoxyresin". It is possible to produce a solvent-free dispersion which iscomparable with the commercial product VEP 2385w but has a markedlyhigher degree of hardness.

It is thus possible, by combining the modification described in DE-A 4327 493 corresponding to CA 2,125,254 with the present invention, toproduce solvent-free dispersions having a markedly improvedcompatibility. The results are reported in Table I.

                                      TABLE I                                     __________________________________________________________________________                    1.2             VEP 2385w                                     Dispersion                                                                             1.1    (comparison)                                                                           1.3    (comparison)                                  __________________________________________________________________________    Notes    styrenized                                                                           polyacrylate                                                                           combination of                                                                       commercial product                                     base resin                                                                           dispersion in epoxy                                                                    1.1 and 1.2                                                          resin dispersion                                              Viscosity                                                                              913 mPa · s                                                                 1480 mPa · s                                                                  1810 mPa · s                                                                1000 mPa · s                         Solids content                                                                         54.5%  56.0%    55.8%  56%                                           Epoxide equivalent                                                                     1013 g/mol                                                                           1078 g/mol                                                                             1213 g/mol                                                                           895 g/mol                                     weight                                                                        Particle size                                                                          820 nm 338 nm   425 nm 650 nm                                        Emulsifier content                                                                     10% on solids                                                                        8% on solids                                                                           8% on solids                                                                         8% on solids                                  Solvent content                                                                        10% on solids                                                                        0%       0%     4.5% on solids                                Pot life 2 h    2 h      2 h    1 h 45 min                                    Dust-dry after                                                                         1 h 15 min                                                                           1 h 30 min                                                                             45 min 30 min                                        Tack-free after                                                                        7 h    8 h      5 h 30 min                                                                           5 h 30 min                                    Leveling*                                                                              0      0        0      0                                             Film cloudiness*                                                                       0      0        0      0                                             Pendulum hardness                                                                      96 sec 48 sec   138 sec                                                                              105 sec                                       after 24 h                                                                    Water resistance*                                                                      1      1-2      0-1    0-1                                           after 24 h                                                                    __________________________________________________________________________     *Evaluation: 0 = very good to 5 = very poor                              

2. Dispersions for heat-curing systems

Synthesis of the base resin modified in accordance with the invention

898 g of the diglycidyl ether of bisphenol A (A1, epoxide equivalentweight about 185 g/mol), 698 g of a product A2 of 1 mol of bisphenol A(A2a) with 2 mol of styrene (A2b) (OH equivalent weight about 220 g/mol)and 304 g of a diglycidyl ether of polypropylene glycol 600 (A1) areheated to 125° C. 1.5 g of Shell® catalyst 1201 are added and then themixture is maintained at 160° C. until an epoxide equivalent weight offrom 760 to 765 g/mol is reached.

2.1 Dispersion according to the invention according to DE 41 28 487corresponding to U.S. Pat. No. 5,236,974

Modified base resin, containing solvent

400 g of the resin according to the invention (2. above) are homogenizedat 80° C. together with 39 g of methoxybutanol and 141 g of a 50%strength aqueous solution of a dispersant B1, as described in DE-A 36 43751 corrsponding to U.S. Pat. No. 4,886,845. The resin is then dispersedwith 258 g of water D by the method described in DE-A 41 28 487corresponding to U.S. Pat. No. 5,236,974.

A storage-stable dispersion is obtained which has the followingcharacteristics:

    ______________________________________                                        viscosity (25° C., Brookfield)                                                             1575 mPa · s                                     residue (1 h/ 1 g, 125° C.)                                                                 56.3%                                                    epoxide equivalent weight                                                                         1614 g/mol                                                (supply form)                                                                 particle size (monomodal)                                                                          650 nm                                                   emulsifier content   15% based on solids                                      solvent content      10% based on solids                                      ______________________________________                                    

2.2 Dispersion according to the invention according to DE-A 43 27 493corresponding to CA 2,125,254

Modified base resin, free of solvent

401 g of the resin according to the invention are homogenized at 80° C.together with 39.6 g of a mixture of styrene, methyl methacrylate andglycidyl methacrylate (C1) (5:4:1) and 122 g of a 50% strength aqueoussolution of a dispersant B1, as described in DE-A 36 43 751corresponding to U.S. Pat. No. 4,886,845. The resin is then dispersedwith 255 g of water D by the method described in DE-A 41 28 487corresponding to U.S. Pat. No. 5,236,974. 0.40 g of tert-butylhydroperoxide and 0.045 g of iron(II) sulfate in the form of a 2%strength aqueous solution are added to the high-solids dispersion at 60°C. This is followed by the continuous addition of a solution of 0.53 gof ascorbic acid in 50 g of water over two hours. After the mixture hasundergone post-polymerization for one more hour at 60° C., a further 35g of water are added.

A storage-stable dispersion is obtained which has the followingcharacteristics:

    ______________________________________                                        viscosity (25° C., Brookfield)                                                             2140 mPa · s                                     residue (1 h, 1 g, 125° C.)                                                                 56.4%                                                    epoxide equivalent weight                                                                         1644 g/mol                                                (supply form)                                                                 particle size (monomodal)                                                                          540 nm                                                   emulsifier content   12% based on solids                                      solvent content       0%                                                      ______________________________________                                    

2.3 Comparison dispersion according to DE-A 41 28 487 corresponding toU.S. Pat. No. 5,236,974

Non-modified base resin, containing solvent

144 g of a polypropylene glycol diglycidyl ether having an epoxideequivalent weight of about 340 g/mol, 231 g of bisphenol A and 525 g ofa diglycidyl ether of bisphenol A having an epoxide equivalent weight of183 g/mol were reacted in accordance with Example 1.2 to give a producthaving an epoxide equivalent weight of 729 g/mol. 900 g of this resinare stirred thoroughly together with 90 g of methoxybutanol. After this,302 g of dispersant (50% in water) are added according to DE-A 36 43751, and dispersion is carried out in the usual manner.

A storage-stable dispersion is obtained which has the followingcharacteristics:

    ______________________________________                                        viscosity (25° C., Brookfield)                                                             1040 mPa · s                                     residue (1 h, 1 g, 125° C.)                                                                 55.1%                                                    epoxide equivalent weight                                                                         1463 g/mol                                                (supply form)                                                                 particle size (monomodal)                                                                          589 nm                                                   emulsifier content   15% based on solids                                      solvent content      10% based on solids                                      ______________________________________                                    

2.4 Comparison dispersion according to DE-A 43 27 493 corresponding toCA 2,125,254

Non-modified base resin, free of solvent

286 g of base resin according to Example 2.3 are homogenized with 121 gof dispersant (50% strength in water) according to DE-A 36 43 751corresponding to U.S. Pat. No. 4,886,845 and 57.2 g of a mixture ofstyrene, methyl methacrylate and glycidyl methacrylate (5:4:1) and thehomogenized mixture is dispersed as usual, the monomers beingpolymerized as in Example 2.2.

A storage-stable dispersion is obtained which has the followingcharacteristics:

    ______________________________________                                        viscosity (25° C., Brookfieid)                                                             1540 mPa · s                                     residue (1 h, 1 g, 125° C.)                                                                 54.0%                                                    epoxide equivalent weight                                                                         2361 g/mol                                                (supply form)                                                                 particle size (monomodal)                                                                          465 nm                                                   emulsifier content   15% based on solids                                      solvent content       0%                                                      ______________________________________                                    

Performance-related properties

The dispersions 2.1 to 2.4 are mixed with one equivalent of anacid-functional water-dilutable curing agent Beckopox® VEM 2436w,catalytic amounts of phosphoric acid are added, and the compositions areknife-coated as clearcoat onto tin plate, dry film thickness 5 μm.Curing is carried out at 200° C. for 12 minutes.

The testing configuration used is the standard testing for can coatings,taking into account pasteurization resistance.

The comparison demonstrates that the compatibility of the resincomponents is considerably improved by the use of the "styrenized epoxyresin". A solvent-free dispersion which was obtained by the methoddescribed in DE-A 43 27 493 corresponding to CA 2,125,254 can beproduced, despite high proportions of styrene in the polyacrylate, incombination with the present invention, with substantially improvedcompatibility, enabling the production of completely solvent-free,pasteurization-resistant beverage can interior coatings. In this case itis even possible to reduce the content of dispersant. The results arereported in Table II.

                                      TABLE II                                    __________________________________________________________________________                                2.3     2.4                                       Dispersion  2.1     2.2     (comparison)                                                                          (comparison)                              __________________________________________________________________________    Notes       "styrenized base                                                                      "styrenized base                                                                      nonmodified                                                                           nonmodified                                           resin"  resin" with                                                                           base resin                                                                            base resin,                                                   polyacrylate    with                                                          dispersion      polyacrylate                                                                  dispersion                                Viscosity   1575 mPa · s                                                                 2140 mPa · s                                                                 1040 mPa · s                                                                 1540 mPa · s                     Solids content                                                                             56.3%   56.4%   55.1%   54.0%                                    Epoxide equivalent weight                                                                 1614 g/mol                                                                            1644 g/mol                                                                            1463 g/mol                                                                            2361 g/mol                                Particle size                                                                              650 nm  540 nm  589 nm  465 nm                                   Emulsifier content                                                                         15% on solids                                                                         12% on solids                                                                         15% on solids                                                                         15% on solids                            Solvent content                                                                            10% on solids                                                                          0%     10%      0% on solids                            Leveling*   0-1     0-1     0-1       3 (haze)                                Double wipes with acetone                                                                  50      50      100     100                                      Pasteurization                                                                            0-1     0-1     0-1     0-1                                       __________________________________________________________________________     *Evaluation: 0 = very good to 5 = very poor                                   Pasteurization: Water, 70° C., one hour                           

While several embodiments of the invention have been described, it willbe understood that it is capable of further modifications, and thisapplication covers any variations, uses, or adaptations of theinvention, following in general the principles of the invention andincluding such departures from the present disclosure as to come withinknowledge or customary practice in the art to which the inventionpertains.

What is claimed is:
 1. A stable, aqueous epoxy resin dispersioncomprising:(A) an epoxy resin formed by condensation of(A-1) at leastone epoxide compound having on average at least two epoxide groups permolecule, with (A-2) an aralkylated or alkylated polyhydroxy aromaticcompound formed by reacting(A-2a) a polyhydroxy aromatic compound with(A-2b) an aromatic or aliphatic compound which carried an alkenyl group;(B) a dispersant; (C) a diluent selected from one or more low molecularweight, liquid, epoxy-functional compounds (C2); and (D) water.
 2. Astable aqueous epoxy resin dispersion as claimed in claim 1, where (A-2)comprises an aralkylated polyhydroxy aromatic compound.
 3. A stable,aqueous epoxy resin dispersion as claimed in claim 1, wherein component(A1) comprises an epoxide compound which has an epoxide equivalentweight of from 100 to 2000 g/mol.
 4. A stable, aqueous epoxy resindispersion as claimed in claim 1, wherein the dispersant (B) comprises acondensation product (B1) of a polyol (B1a) and an epoxide compound(B1b) having at least two epoxide groups per molecule.
 5. A stable,aqueous epoxy resin dispersion as claimed in claim 4, wherein thedispersant (B) additionally comprises at least one surfactant (B2).
 6. Astable, aqueous epoxy resin dispersion as claimed in claim 1, which isfree from organic solvent.
 7. A stable, aqueous epoxy resin dispersionas claimed in claim 1, wherein the average particle size of thedispersed resin is less than 1 μm.
 8. A stable, aqueous epoxy resindispersion as claimed in claim 4, wherein the dispersant comprises acondensation product (B1) of a polyetherpolyol (B1a) and a polyglycidylether (B1b).
 9. A stable, aqueous epoxy resin dispersion as claimed inclaim 1, which further comprises an addition polymer formed fromolefinically unsaturated monomers.
 10. A stable, aqueous epoxy resindispersion as claimed in claim 1, which additionally comprises one ormore organic solvents.
 11. A stable, aqueous epoxy resin dispersioncomprising:(A) an epoxy resin formed by condensation of(A-1) at leastone epoxide compound having on average at least two epoxide groups permolecule, with (A-2) an aralkylated or alkylated polyhydroxy aromaticcompound formed by reacting(A-2a) a polyhydroxy aromatic compound with(A-2b) an aromatic or aliphatic compound which carried an alkenyl group;(B) a dispersant; (C) an addition polymer prepared by free-radicalpolymerization of olefinically unsaturated monomers (C1) in the presenceof epoxy resin (A); (D) water.
 12. A stable aqueous epoxy resindispersion as claimed in claim 11, wherein the polymer (C) is preparedby the polymerization of monomers (C1) with one or more free-radicalinitiators in the presence of a dispersion of the epoxy resin (A) inwater (D).
 13. A stable, aqueous epoxy resin dispersion as claimed inclaim 11, wherein the ratio by mass of epoxy resin (A) to the additionpolymer (C) is from 99.5:0.5 to 20:80.
 14. A process for the preparationof a stable, aqueous epoxy resin dispersion as claimed in claim 11,which comprises:preparing an epoxy resin (A) from the epoxide compound(A1) and the aralkylated polyhydroxy aromatic compound (A2), dispersingthe modified epoxy resin (A) in water with the addition of a dispersant(B) and of at least one olefinically unsaturated monomer (C1), andpolymerizing (C1) by adding a radical-forming initiator to form additionpolymer (C).
 15. A process as claimed in claim 14, where in addition tothe monomers (C1), at least one substance is added to epoxy resin (A)which is selected from low molecular weight, liquid epoxide compounds(C2) and inert organic solvents (C3), conjointly with, prior to, orfollowing the addition of the monomer (C1).
 16. A stable, aqueous epoxyresin dispersion as claimed in claim 11, wherein the dispersant (B)comprises a condensation product (B1) of a polyol (B1a) and an epoxidecompound (B1b) having at least two epoxide groups per molecule.
 17. Astable, aqueous epoxy resin dispersion as claimed in claim 16, whereinthe dispersant comprises a condensation product (B1) of apolyetherpolyol (B1a) and a polyglycidyl ether (B1b).
 18. A stableaqueous epoxy resin dispersion as claimed in claim 11, where (A-2)comprises an aralkylated polyhydroxy aromatic compound.
 19. A stableaqueous epoxy resin dispersion as claimed in claim 11, where theolefinically unsaturated monomers (C1) contain functional groups capableof curing the epoxy resin (A).
 20. A stable aqueous epoxy resindispersion as claimed in claim 11, wherein the epoxy resin (A) is cured.21. A stable aqueous epoxy resin dispersion as claimed in claim 11,wherein (A-2b) is an aromatic compound which carried an alkenyl group.22. A stable aqueous epoxy resin dispersion as claimed in claim 11,wherein (A-2b) is an aromatic compound which carried an alkenyl group.23. A stable aqueous epoxy resin dispersion as claimed in claim 1,wherein (A-2b) comprises an aliphatic compound selected from vinylesters, vinyl ethers, esters of acrylic or methacrylic acid withmonoalcohols having 1 to 18 carbon atoms, or hydroxyl C₂ - to C₄ - alkyl(meth)acrylates.
 24. A stable aqueous epoxy resin dispersion as claimedin claim 11, wherein (A-2b) comprises an aliphatic compound selectedfrom vinyl esters, vinyl ethers, esters of acrylic or methacrylic acidwith monoalcohols having 1 to 18 carbon atoms, or hydroxyl C₂ - to C₄ -alkyl (meth)acrylates.
 25. A stable epoxy resin dispersion as claimed inclaim 1, wherein the mass of component (C2) is from 1 to 25% based onthe sum of the masses of components (A) and (C).
 26. A stable epoxyresin dispersion as claimed in claim 1, wherein the diluents (C2) areselected from the group consisting of para-tert, butylphenyl glycidylether, n-butyl glycidyl ether, phenyl glycidyl ether, ortho-cresylglycidyl ether, butanediol diglycidyl ether, hexanediol diglycidylether, neopentylglycol diglycidyl ether, dimethylolcyclohexanediglycidyl ether, 2-ethylhexyl glycidyl ether, versatic acid glycidylester, and the diglycidyl ethers of bisphenol A and bisphenol F.